Using High Brightness LCD as Outdoor Signage

By Hank Liu 

LED technology has long been considered the answer for using digital signage in outdoor environments, but LCD is coming outside and offering what may be a better, compromise-free solution.

Mainstream outdoor LED displays – the kind you see on highway billboards, big public plazas and sports stadiums – have the unique advantage of being as big as they need to be, and bright enough to shine through even the brightest sunlight.

But they’re meant to be viewed at a distance – because the individual light emitting diodes (that’s the L, E and D of LEDs) – are spaced apart from each other on the display surface. A billboard in Times Square, for example, looks amazing when viewing from street-level. Up close, all those light pixels no longer look seamless, and the viewing experience can be somewhere between bad and awful.

There are fine pixel pitch LED displays available now, that pack many more light pixels into a display surface, but all that extra lighting adds much more capital cost, and raises operating energy costs because each little light draws power. A fine pitch LED screen can cost three to five times as much as an LCD of the same dimension.

Even at 2.5mm, the minimum benchmark for what’s called fine pitch LED, a screen is best viewed from 20 feet or more distance.

LCD technology doesn’t have that viewability problem. An LCD screen looks amazing up close, or at a distance. But until recently, typical commercial LCDs have not had the levels of brightness needed to be used outdoors in direct sunlight.

That’s changed.

In recent years, LCD makers have begun developing screens that are more adaptable for outdoor use. It’s not an easy task.

LCDs are made by a complicated semiconductor manufacturing process involving sensitive and delicate equipment, chemicals and materials. In order for the liquid crystals and other materials to withstand the heat coming from the backlight modules, as well as the sunlight, special manufacturing techniques and materials are needed.

A commercial LCD display – even an extra-bright one – that is designed for indoor use should stay inside.

Outdoor LCDs are customized for amplified backlight modules, have special engineering to handle and exhaust heat, and are both weather-sealed and ruggedized.

High-brightness LCDs are IP66 certified (dust-tight and capable of withstanding a high-pressure water spray), and are rated for a minimum of five years of continuous use.

Another advantage of high-brightness LCDs is that they are fundamentally similar to other standard LCDs, including the full availability of RS232 functions. This means that the brightness can be adjusted by time of day, or even by ambient light sensors that make the screen only as bright as it needs to be.

This not only reduces energy consumption and costs, but means a screen in a shop window is not blindingly bright at night, when that’s not necessary. But at 2 PM on a sunny day, that brightness can make the difference of cutting through the glare of direct sunlight.

Smaller LED poster-style displays that approximate the dimensions of LCD displays are emerging in the digital signage marketplace, but they can’t begin to match the resolution of a full or 4K LCD. It’s like asking advertisers to produce material in low resolution standard definition formats, ignoring that consumers are now conditioned to seeing HD.

Only a few manufacturers produce the cells that are custom-made for high-brightness LCDs. At AU Optronics, we currently offer high quality, high-brightness LCD displays in sizes such as 46” (1,500 nits) and 55” (2,500 nits).

These screens are being actively used for outdoor applications such as windows displays, gas stations, public smart city kiosks, bus stops, and charging stations.

Bright, crisp outdoor LCD displays probably won’t ever have the dimensions to compete with or replace those jumbotron LEDs. But they offer a viewing experience, particularly up close and personal, that LED technology may never match.

About the Author:

Hank was born and raised in Taipei, Taiwan, but moved to the U.S. He graduated from the University of Washington and the Penn State Dickinson School of Law. After passing the bar exam, he went back to Taiwan and worked in a law firm focusing on commercial banking. He joined AUO in 2004, and was AUO’s General Counsel until 2017. He then moved to AUO’s strategic investments team.